php使用mysql_connect、mysqli和pdo连接mysql返回的数据都是字符串格式

 1 error_reporting(E_ALL & ~E_NOTICE & ~E_DEPRECATED);
 2 $con = mysql_connect("127.0.0.1","root","root");
 3 if (!$con)
 4 {
 5     die('Could not connect: ' . mysql_error());
 6 }
 7 mysql_select_db("test", $con);
 8 $result = mysql_query("SELECT * FROM test_oo");
 9 
10 while($row = mysql_fetch_array($result))
11 {
12     // echo gettype($row['id']) . "--" . gettype($row['smallint']);
13     echo "<br />";
14     var_dump($row['id']);
15     if(is_int($row['id']))
16     {
17         echo 'int';
18     }elseif(is_string($row['id']))
19     {
20         echo 'string';
21     }
22 }

$con=mysqli_connect("localhost","root","root","test"); 
// 检查连接 
if (!$con) 
{ 
    die("连接错误: " . mysqli_connect_error()); 
} 
$result = mysqli_query($con,'select * from test_oo');
$arr = mysqli_fetch_array($result,MYSQLI_ASSOC);
var_dump($arr);

 1 error_reporting(E_ALL & ~E_NOTICE & ~E_DEPRECATED);
 2 $user = 'root';
 3 $pass = 'root';
 4 try {
 5     $dbh = new PDO('mysql:host=localhost;dbname=test', $user, $pass);
 6     foreach($dbh->query('SELECT * from test_oo') as $row) {
 7         print_r($row);
 8         echo '<br>';
 9         settype($row['id'],'int');
10         echo gettype($row['id']);
11         echo '<br>';
12     }
13     $dbh = null;
14 } catch (PDOException $e) {
15     print "Error!: " . $e->getMessage() . "<br/>";
16     die();
17 }